Solids exclusion device for a seal chamber

ABSTRACT

A solids excluder device is mountable within a seal chamber to protect a shaft structure, such as a mechanical seal. The excluder device fits within a conventional seal chamber and circumferentially surrounds a shaft wherein the bushing includes circulation inducing formations which face towards a shaft surface and generate a flow of process fluid away from the mechanical seal or other pump components. The excluder bushing prevents the accumulation of solids within the seal chamber by generating a flow of process fluid out of this seal chamber. The flow carries solid particulates and other solid contaminants out of the seal chamber and away from the mechanical seal or other pump components to prevent the accumulation of solids within the seal chamber.

FIELD OF THE INVENTION

The invention relates to a solid exclusions device for use with a rotating shaft of industrial equipment and more particularly, to a solids exclusion device for use with and the protection of a mechanical seal.

BACKGROUND OF THE INVENTION

Conventional equipment used in an industrial environment include compressors, pumps, mixers and the like. Such equipment typically includes a rotating shaft driven by a motor and a shaft driven component, such as the pump impeller. These driven components such as the pump impeller are rotated at high speeds to effect movement of a process fluid, for example, within the piping of an industrial facility. In the case of pumps, the process fluid is a liquid that is moved by the pumps through a fluid handling system and the piping thereof.

To prevent leakage of the process fluid along the rotating shaft of the equipment, it is well known to provide mechanical seals within the equipment which mechanical seals surround the rotating shaft and prevent or significantly minimize fluid leakage along the shaft surface. Typically, such mechanical seals include a pair of opposed annular seal rings which surround the shaft wherein one seal ring is non-rotatably supported on a seal housing while the other rotatable seal ring is mounted to the shaft and rotates therewith. The seal rings include opposed seal faces which typically extend radially outwardly from the shaft surface and face axially toward each other in sealing engagement to define a sealing region extending radially between these opposed seal faces. Such seal faces may be disposed in contacting relation in a contacting type mechanical seal and more preferably, may include seal face features which cause seal face separation during shaft rotation in non-contacting type mechanical seals.

When the mechanical seal is mounted to the rotating equipment, the seal rings are disposed within or adjacent to a seal chamber of the pump or other such equipment which seal chamber is in open fluid communication with another process fluid chamber such as an impeller housing of a pump. As such, the process fluid is able to flow into the seal chamber. Such seal chambers also are known as packing boxes or stuffing boxes.

Furthermore, process fluids such as pumped liquids often include solid particulates which solids are able to flow into the seal chamber in the region directly adjacent to the seal rings. A problem encountered under such conditions is that solids may accumulate in the seal chamber and cause clogging of the seal components, erosive or abrasive wear of the seal rings, and seal face overheating during shaft rotation which may cause early equipment failure and costly downtime.

It is known to attempt to reduce the negative impact of such solids accumulation by providing a flushing system wherein an external clean fluid is supplied to the seal chamber adjacent to the seal rings to attempt to flush out the solids although this results in additional system components and maintenance and additional costs for these components and the water supplied thereto as the flush liquid.

It is an object of the invention to overcome the disadvantages associated with known systems resulting from the accumulation of solids in a seal chamber.

The invention therefore relates to a solids excluder device or bushing which is mountable within a seal chamber to redirect the solids out of the seal chamber and minimize if not eliminate the accumulation of such solids within the seal region. This thereby avoids the erosion and wear of the seal components and the shaft sleeve, and the negative impact that this wear may have on seal operation.

More particularly, the solids exclusion device is an excluder bushing which fits circumferentially around the shaft in coaxial relation therewith. The excluder bushing is disposed on the process fluid side of the seal rings and includes circulation inducing formations on the inner circumferential side of the excluder bushing which generate a flow or circulation of the process fluid out of the seal chamber. This fluid flow flushes and carries solids within the process fluid away from the seal chamber and back into the impeller housing or other adjacent chamber.

The circulation inducing formations preferably are in the form of flow slots or channels formed in the inside circumferential side of the bushing. The flow slots include circumferential slots which extend circumferentially and preferably are generally parallel to each other so as to be separated by circumferential slot walls disposed between adjacent pairs of the slots. The slot walls also are provided with tangentially angled scarf slots or channels which angle circumferentially and axially in open communication between each axially adjacent pair of circumferential slots.

As a result of viscous flow generated by rotation of the shaft and specifically the circumferential movement of the shaft surface adjacent to the excluder bushing, a flow of process fluid is generated which flows circumferentially or tangentially and also axially away from the seal rings. The excluder bushing thereby pushes solids away from the seal rings while allowing a return flow of cleaner process fluid which travels axially toward the seal rings along the shaft surface. As a result, the excluder bushing of the invention is able to remove solids from the seal chamber without requiring a separate cleansing flush and the additional equipment required therefor. A flush system may be completely eliminated although one may still be provided while the flush rate may be reduced.

As a result, disadvantages associated with known systems are reduced if not eliminated such that the excluder bushing of the invention provides advantages over known systems.

Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross-sectional view of a unit of equipment having a rotatable shaft, an equipment housing and a mechanical seal mounted to the equipment housing for sealing the shaft.

FIG. 2 is a cut-away outer end view of a seal chamber, the shaft and a solids excluder device or bushing disposed in the seal chamber.

FIG. 3 is an inboard end view of the solids excluder bushing showing two bushing halves which are mated together and configured for shaft rotation in the counter-clockwise as viewed from the process end of the shaft.

FIG. 4 is a side view of the left bushing half illustrating fluid flow slots therein.

FIG. 5 is an enlarged partial end view of an alignment pin on the right bushing half.

FIG. 6 is an interior end view of the excluder bushing with the flow slots illustrated in phantom outline.

FIG. 7 is a side view of the right bushing half.

FIG. 8 is an isometric view of the right bushing half.

FIG. 9 is an interior end view of an excluder bushing configured for clockwise shaft rotation.

FIG. 10 is a side view of the left bushing half of the excluder bushing of FIG. 9.

FIG. 11 is an enlarged partial end view of the alignment pin therefor.

FIG. 12 is an interior end view of a clockwise excluder bushing with flow slots illustrated in phantom outline.

FIG. 13 is a side view of the left bushing half of FIG. 12.

FIG. 14 is a side cross-sectional view of a reduced-length excluder bushing in a short seal chamber.

FIG. 15 is an interior end view of the reduced length excluder bushing configured for counter-clockwise shaft rotation.

FIG. 16 is a side view of the left bushing half of the excluder bushing of FIG. 15.

FIG. 17 is an enlarged partial end view of the alignment pin therefor.

FIG. 18 is an interior end view of the reduced length excluder bushing with the flow slots illustrated in phantom outline.

FIG. 19 is a side view of the right bushing half.

FIG. 20 is an interior end view of a reduced length excluder bushing configured for clockwise shaft rotation.

FIG. 21 is a side view of the left bushing half.

FIG. 22 is an enlarged end view of the alignment pin therefor.

FIG. 23 is an interior end view of the excluder bushing of FIG. 20 with the flow slots illustrated in phantom outline.

FIG. 24 is a side view of the right bushing half.

Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, the invention relates to a solids excluder bushing 10 which is adapted for installation within the process fluid housing 12 of industrial equipment 14, which equipment includes a rotatable shaft 15 extending longitudinally therethrough.

More particularly, the equipment 14 is of any known conventional equipment which incorporates a rotatable shaft 15 and wherein use of the solids excluder bushing 10 would be appropriate. Preferably, the equipment 14 comprises a pump wherein the process fluid housing 12 is an impeller housing in which a rotatable impeller 16 (FIG. 2) is fixed to the interior end of the rotatable shaft 15 and rotatably driven thereby. This impeller 16 and housing 12 are well known and a detailed discussion thereof is not required. The outboard end 18 of the shaft is connected to and driven by a pump motor (not illustrated) which again has a conventional construction.

Referring to FIG. 1, the housing 12 includes an interior process fluid chamber 20 in which the impeller 16 (FIG. 2) is disposed wherein this chamber has a process fluid 20A which is a liquid when the equipment 14 comprises a pump. This process fluid 20A is pumped throughout a fluid handling system through rotation of the impeller 16 by the shaft 15.

The housing 12 includes an axially extending annular flange 21 which terminates at an end wall 22 and defines a cylindrical seal chamber 23 therein. The seal chamber 23 also is conventionally known as a packing box or stuffing box.

The seal chamber 23 is defined by an interior surface 24 which faces radially inwardly towards the outer shaft surface 25 that defines the outer diameter (OD) of the shaft 15. A radial space thereby is defined by the shaft OD which is disposed in opposing relation with the interior chamber surface 24 wherein the radial space has a constant radial dimension along its axial length. The outboard end or motor side of this seal chamber 23 opens axially along the length of the shaft 15 while the inboard end or process side thereof is partially enclosed by a radial housing wall 27 which extends radially inwardly. The housing wall 27 has an interior wall surface 28 (FIG. 2) that faces radially inwardly towards the opposing shaft surface 25. This inner wall surface 28 and the opposing shaft surface 25 define a narrow gap 29 (FIG. 1) which allows the process fluid to be able to flow axially into and out of the seal chamber 23.

Accordingly, to sealingly enclose the open end of the seal chamber 23, a mechanical seal 30 is mounted to the outboard end of the pump housing 21 as seen in FIG. 1.

The mechanical seal 30 may have any conventional configuration and in the illustrated embodiment of FIG. 1 is shown as a single seal. This mechanical seal 30 thereby serves to prevent leakage or at least minimize leakage of process fluid 20A along the exterior surface 25 of the shaft 15.

The mechanical seal 30 includes a seal housing 31 that is rigidly affixed to the pump housing 12 and supports an annular seal ring 32 thereon. The annular seal ring 32 is biased axially by a plurality of springs 33 so as to effectively float axially during operation.

The mechanical seal 30 further includes a shaft sleeve 35 which is rigidly affixed to the shaft 15 in a conventional manner so as to rotate in unison therewith. This shaft sleeve 35 supports an additional rotatable seal ring 36 which cooperates axially against the stationary seal ring 32. The opposing seal rings 32 and 36 have opposed seal faces which extend radially and face axially toward each other to define a seal region therebetween. The seal rings 32 and 36 may be configured either for contacting operation or non-contacting operation, for example, if provided with hydrodynamic lift features, such as spiral grooves or the like.

During operation, the seal ring 32 remains stationary while the adjacent seal ring 36 rotates with the shaft 15. The seal rings 32 and 36 thereby separate an outer chamber 40 which receives process fluid therein from an inner chamber 41 that is disposed along the outer shaft surface 25 and communicates with atmosphere in the illustrated embodiment. If desired, the mechanical seal 30 could be configured as a double seal wherein the inner chamber 41 accommodates a buffer fluid or barrier fluid.

Due to the existence of the process fluid within this outer seal chamber 40, the solids excluder device or bushing 10 of the invention is provided to prevent the accumulation of solids and other particulates within this outer chamber 40 and the region directly adjacent to the seal rings 32 and 36. Where such build up of solids and other contaminants occurs in known seals, such solids and contaminants may generate erosive or abrasive wear of the seal rings within this region. This may ultimately affect the seal life of the mechanical seal 30 and cause premature wear and degradation of the seal operation. Generally, the solids excluder bushing 10 of the invention is able to redirect and generate a flow of process fluid out of the seal chamber 23 which flow carries the solids and contaminants out of this chamber and draws such substances away from the sealing region.

Generally referring to FIGS. 1-3, the excluder bushing 10 preferably is radially split into left and right bushing halves 45 and 46 that couple together to define an outer circumferential surface 47. The outer surface 47 is disposed closely adjacent to the interior chamber surface 24 so that the excluder bushing 10 may be slid axially into the seal chamber 23 during installation. Since the bushing 10 is formed of the left and right halves 45 and 46, these halves may be installed separate from each other on opposite sides of the shaft 15 so as to encircle a pre-existing shaft 15 and then when mated together into the configuration of FIGS. 2 and 3, the bushing 10 may be slid axially into the seal chamber 23 in tight-fitting engagement therewith.

To maintain the bushing 10 in position within the chamber 23, the outer bushing surface 47 is formed with a circumferential groove 48 in which is disposed a split elastomeric body preferably formed as O-ring 49, which O-ring 49 projects radially outwardly a small distance so as to snugly fit against the inside chamber surface 24. This O-ring 49 primarily serves to secure the bushing ring 10 within the seal chamber 23 and prevent rotation of the bushing 10 during shaft rotation. Preferably, the O-ring 49 is a fluoroelastomer which is selected so as to withstand the specific process fluid and avoid deterioration or corrosion of the O-ring 49 by this process fluid.

Generally, the bushing halves 46 and 47 have a half-circle shape so that when assembled together as seen in FIG. 3, the bushing 45 has an annular, closed-loop configuration defined by the outer circumferential surface 47 and an inner circumferential surface 51. This inner circumferential surface 51 is disposed closely adjacent to the outer shaft surface 25 as seen in FIG. 1 to provide a limited clearance space therebetween which still permits the migration of process fluid 20A along the shaft surface 25 into the outer seal chamber 40.

Preferably, each of the bushing halves 45 and 46 is formed from a corrosion and abrasion resistant material. Preferably, the bushing halves 45 and 46 are formed from glass filled polytetrafluorethylene (GF PTFE) which provides a high degree of chemical and wear resistance. This standard material is particularly suitable for the paper industry wherein the process fluid 20A may include significant amounts of highly fibrous media. For highly abrasive media such as those found in municipal industries, the bushing halves 45 and 46 may be formed from polyethyl ether ketone (PEEK).

The process fluid for these exemplary industries, namely the paper industry or municipal industries, often include solids therein mixed in with the liquid being pumped. As discussed above, these solids may ordinarily migrate into the seal chamber 23 of the pump or migrate further into the outer chamber 40 of the mechanical seal 30 and negatively impact the performance of the seal rings 32 and 36. Therefore, the solids excluder bushing 10 is provided to generate a circulation or flow of the process fluid 20A out of the seal chamber 23 which flow therefore draws the solids away from the seal rings 32 and 36 and serves to protect these seal components and optimize the continued performance of these components. Generally, the bushing 10 is provided with flow inducing formations 55 in the inner bearing surface 51 which formations 55 are configured to generate a combination of a circumferential process fluid flow and an axial process fluid flow which angles tangentially within the flow formations 55 to thereby cause circulation of the process fluid 20A back into the process fluid chamber 20.

More particularly as to the flow formations 55, the left and right bushing sections preferably defined as halves 45 and 46 are illustrated respectively in FIGS. 4 and 7.

First as to the left bearing half 45 (FIG. 4), this bearing half 45 includes a plurality and preferably two continuous circumferential flow slots 56 and 57 which are respectively provided on the outboard bushing end 58 and the inboard bushing end 59. These flow slots 56 and 57 open radially inwardly and extend radially outwardly to the outer circumferential bushing wall 60. It will be understood that the bushing halves 45 and 46 each define a respective one half of each of these slots 56 and 57 and the outer bushing wall 60 with common reference numerals being used in FIGS. 4 and 7 for these structures.

The bushing halves 45 and 46 further include continuous interior flow slots 61 and 62 which extend circumferentially parallel to the outer slots 56 and 57 wherein these slots 56, 57, 61 and 62 are separated from each other by circumferentially extending slot walls 63, 64 and 65. These slot walls 63, 64 and 65 project radially inwardly from the bushing wall 60 and define the inner circumferential surface or inside face 51 of the bushing 10. As such, the bushing 10 illustrated in FIGS. 3-8 has two outer slots 56 and 57 and two interior slots 61 and 62 wherein the axial length of the bushing 10 is adapted for a seal chamber 23 having a longer length as compared to variations of the inventive bushing illustrated in further detail herein.

When the bushing halves 45 and 46 are joined together, the portions of the circumferential or tangential flow slots 56, 57, 61 and 62 defined by the respective bushing halves 45 and 46 are circumferentially and axially aligned. To ensure alignment of the bushing halves 45 and 46, the left bushing half 45 is provided with an alignment bore 70 proximate to the outboard bearing end 58.

As will be discussed in further detail herein, the circumferential slots 58, 59, 61 and 62 generate a circumferential flow of process fluid 20 through these slots during shaft rotation. In addition to this circumferential flow, the bushing half 45 and 46 also induce tangentially angular flow of the process fluid 20 from each circumferential slot to the next circumferential slot disposed axially adjacent thereto. This tangentially angled flow is induced by a plurality of angled scarf cuts provided in the slot walls 63, 64 and 65.

More particularly, in the left bushing half 45, a scarf cut 72 is provided through the center slot wall 64. This scarf cut 72 extends circumferentially at an angle from an upstream end 73 to a downstream end 74 as seen in FIGS. 4 and 6. Thus, during circumferential flow within the slot 61, the process fluid 20 and in particular, the solids carried thereby flow through this scarf cut 72 toward the next outwardly adjacent slot 62 as indicated by reference arrow 75 (FIG. 4).

Referring to the right bushing half 46 (FIG. 7), this bushing half includes additional scarf cuts 78 and 79 which angle through the outer slot walls 63 and 65. The outboard scarf cut 78 extends between opposite open ends 80 and 81 and defines the entrance through which the process fluid 20A flows from the outermost slot 56. This fluid then flows into the next adjacent circumferential slot 61 which fluid is then able to flow to the slot 62 through the scarf cut 72 (FIG. 4) in the outer bushing half 45. The fluid then may flow from this circumferential slot 62 through the inboard scarf cut 79 and specifically from the upstream end 82 to the downstream end 83 in the direction of arrow 84. The flow through the outboard scarf cut 78 also flows at an angle as indicated by reference arrow 85 in FIG. 7.

This cut opening 83 thereby defines the exit port through which the process fluid 20A and associated solids flows back into the process fluid chamber 20 described above.

When assembled together as seen in FIGS. 3 and 6, the various circumferential flow slots 56, 57, 61 and 62 are circumferentially aligned wherein the right bushing half 46 includes alignment pins 90 (FIG. 8) that seat within the aligned alignment bores 70 (FIGS. 4 and 6). With this construction, the bushing 10 is provided with a plurality of circumferential flow slots 56, 57, 61 and 62 wherein axially adjacent pairs of such slots communicate with each other by tangentially angled scarf cuts, i.e. angled flow slots, 72, 78 and 79. This combination of flow slots defines a labyrinth like flow path for the flow of process fluid.

During shaft rotation, a viscous flow of the process fluid 20A is induced through the various flow slots wherein the direction of the scarf cuts 72, 78 and 79 causes this viscous flow to eventually move the process fluid 20A and the associated solids axially away from the seal rings 32 and 36. In this regard, the excluder bushing 10 is configured to accommodate counterclockwise rotation of the shaft 15 as indicated by reference arrows 91 and 92 and FIGS. 3-8. This reference to counterclockwise rotation of the shaft 15 is the direction of the rotation of the shaft 15 when viewed from the inboard end or process side thereof. If the shaft 15 is viewed from the outboard end or motor side, such shaft rotation would be deemed to be clockwise rotation. With reference to the associated drawings, the shaft rotation is identified when the shaft 15 is viewed from the inboard shaft end.

With respect to FIGS. 9-13, an alternative excluder bushing 10-1 is illustrated which is configured for clockwise shaft rotation as indicated by reference arrows 91-1 and 92-1. In this regard, the bushing 10-1 includes an outer bushing wall 60-1 which includes substantially the same flow inducing formations 55-1 as described above except that the angled slot formations are configured for clockwise shaft rotation.

Generally, the bushing wall 60-1 includes a plurality and preferably three radially projecting slot walls 63-1, 64-1 and 65-1 which define outer slots 56-1 and 57-1 adjacent to a respective outboard bushing end and 58-1 and an inboard bushing end 59-1. Additional interior slots 61-1 and 62-1 are formed substantially identical to the above described slots.

For reference purposes, the same common reference numerals are used for common structural features of the bushings 10 and 10-1 with the suffix “-1” included therewith to differentiate the structures of FIGS. 3-8 from the structures of FIGS. 9-13.

The left and right bushing halves 45-1 and 46-1 are configured for alignment by alignment pins 90-1 (FIG. 11 and FIG. 12) such that the circumferential flow slots 61-1 and 62-1 extend continuously and each define a continuous annular passage. The primary difference between the bushings 10 and 10-1 is the angular direction of the scarf cuts 72-1 (FIG. 10) and the scarf cuts 78-1 and 79-1 (FIG. 13). In this regard, the scarf cuts 72-1, 78-1 and 79-1 extend in an opposite angular direction relative to the above-described scarf cuts 72, 78 and 79 to generate a tangentially angled fluid flow that extends in the opposite angular direction as indicated by reference arrows 75-1, 84-1 and 85-1 of FIGS. 10 and 13. This angular flow between the two bushings 10 and 10-1 is still the same in that this flow displaces the process fluid and the associated solids axially away from the seal rings 32 and 36. Due to the opposite clockwise rotation of the shaft 15 is indicated by reference arrows 91-1 and 92-1, these scarf cuts 75-1, 78-1 and 79-1 have an opposite angular orientation. With this arrangement, the bushings 10 and 10-1 have substantially the same construction but are configured for different rotation directions of the shaft 15.

Referring to a further embodiment illustrated in FIG. 14, some equipment environments have a smaller space in which the solids excluder bushing may be fitted, thus necessitating the construction of an alternative embodiment of the inventive bushing which is able to accommodate short seal chambers. More particularly, FIG. 14 illustrates a similar arrangement of equipment 14 having an equipment housing 100 with a seal chamber 101 formed therein. A rotatable shaft 102 is provided wherein a passage 103 is defined between the housing 100 and the shaft 102 to allow for rotation of the shaft 102 which also allows for the passage of process fluid from an equipment chamber 104 into the seal chamber 101.

The above-described mechanical seal 30 is mounted thereto to seal the shaft 102. The mechanical seal 30 is illustrated as being cut through an alternative location such that the seal housing 31 has a slightly different appearance from that illustrated in FIG. 1. It will be understood that the mechanical seal 30 illustrated in FIGS. 1 and 14 is still the same. Generally, this mechanical seal includes the same seal rings 32 and 36 disposed in opposed sealing relation with the seal ring 32 non-rotatably supported on the seal housing 31, and the seal ring 36 supported by shaft sleeve 35 for rotation in unison with the shaft 102.

To accommodate the reduced dimension seal chamber 101, a further shorter length solids excluder bushing 110 is illustrated therein. This excluder bushing 110 has an outer bushing wall 111 which receives a split O-ring 112 therein for frictional engagement with the inside surface 113 of the seal chamber 101.

Referring more particularly to the reduced length excluder bushing 110, this bushing 110 is illustrated in further detail in FIGS. 15-19. The excluder bushing 110 is substantially similar to the bushing 10 described above in that it is adapted for counter-clockwise rotation as indicated by reference arrows 115 and 116. The excluder bushing 110 is defined by left and right bushing halves 117 and 118 which are formed with flow inducing formations 119 therein. These flow formations 119 still have a similar combination of circumferential slots and tangentially angled scarf cuts but the overall number of such structures is reduced due to the reduced axial length of the modified excluder bushing 110.

More particularly, the bushing halves 117 and 118 are provided with axially shallow circumferential slots 120 and 121 adjacent to the respective outboard bushing end 122 and inboard bushing end 123. An additional intermediate circumferential flow slot 124 is provided which flow slot 124 is separated from the outer slots 120 and 121 by circumferential slot walls 126 and 127.

To effect the flow of process fluid therethrough, the slot wall 126 of the right bushing half 118 of FIG. 19 includes an angled scarf cut 128 (FIG. 19) which has upstream end 129 and a downstream end 130 and generates an angled fluid flow 131 therethrough. Thus, during counter-clockwise shaft rotation of the shaft 102 in the direction of arrow 115 (FIG. 19) the scarf cut 128 induces a flow of process fluid 20A in the direction of reference arrow 131 from the upstream end 129 for subsequent discharge through the downstream end 130 into the circumferential groove 124.

Referring to FIG. 16, the other left bushing half 117 has a scarf cut 135 which is tangentially angled and passes through the slot wall 127 to permit discharge of process fluid 20A from the circumferential slot 124. This scarf cut 135 has an upstream end 136 and a downstream end 137 which generates a fluid flow in the direction of reference arrow 138 for discharge of the process fluid back through the passage 103 (FIG. 14).

Similar to the bushing embodiments described above, the right bushing half 118 includes alignment pins 140 projecting from the end faces thereof for engagement with alignment bores 141 provided in the left bushing half 117.

Additionally, the outer bushing wall 111 includes a circumferential O-ring slot 142 in which the O-ring 112 is received. In this manner, the excluder bushing 110 is frictionally seated within the seal chamber 101 and functions substantially similar to the excluder bushing 10 described above.

Additionally, a reduced length excluder bushing 110-1 (FIGS. 20-24) may be configured for clockwise rotation as indicated by reference arrows 145 and 146. The excluder bushing 110-1 is formed of left and right bushing halves 117-1 and 118-1. The bushing halves 117-1 and 118-1 are formed with substantially similar circumferential slots 122-1 and 123-1 along with the intermediate circumferential flow slot 124-1. These slots are separated by slot walls 126-1 and 127-1 to axially separate the circumferential flow slots one from the other. These circumferential slots are maintained in alignment by a similar arrangement of alignment pins 140-1 and corresponding bores 141-1 (FIG. 22) which serve to align the left and right bushing halves 117 and 118.

To generate a tangentially angled flow between the parallel circumferential slots, a similar arrangement of scarf cuts or tangentially angled flow slots are provided. In particular, the left bushing half 117-1 (FIG. 21) includes a scarf cut 135-1 having an upstream end 136-1 and a downstream discharge end 137-1 which generates a fluid flow in the direction of reference arrow 138-1 during clockwise rotation of the shaft 102.

Referring to FIG. 24, a further scarf cut 128-1 has an upstream input end 129-1 and a downstream discharge end 130-1 and generates tangentially angled fluid flow in the direction of reference arrow 131-1 during clockwise shaft rotation. During this rotation, the process fluid and associated solids enter the angled scarf cut or flow slot 128-1 through the upstream end 129-1 of the scarf cut 128-1 and ultimately is discharged through the downstream end 137-1. Here again the excluder bushing 110-1 like the other excluder bushings 10, 10-1 and 110 all generate a solids-removing fluid flow through the combination of circumferential flow slots and tangentially angled flow slots. While this generates a fluid flow out-of the seal chamber 23 or 101, the process fluid is able to flow or circulate back into the seal chambers 23 and 101 through the radial gap defined between the interior circumferential surface of the excluder bushings and the outer shaft surface. This return flow of process fluid is cleaner in that the solids are being flushed out through the excluder bushings and the concentration of solids is maintained at a lower level next to the seal rings 32 and 36 than what would otherwise occur if solids were permitted to build up within the seal chambers adjacent to the sealrings 32 and 36.

With the excluder bushings of the invention, a clean flush may be eliminated from the process fluid side of the mechanical seal 30. However, this cleansing flush may still be provided and may even be preferred to supplement the inventive excluder bushings and ensure optimum environmental conditions for the mechanical seal 30. With the excluder bushing and the fluid flow generated thereby, the cleansing flow may be reduced as compared to a cleansing flow provided in the absence of an excluder bushing.

While the bushing of the invention is provided in combination with the mechanical seal 30 to protect the shaft components thereof, the excluder bushing also may be provided adjacent to other shaft components and types of seals to project these components and prevent or at least minimize the build up of process fluid solids adjacent thereto.

In use, the excluder bushings 10, 10-1, 110 or 110-1 are selected based upon the size of the seal chamber 23 or 101 and the direction of shaft rotation. Once the excluder bushing design is selected, the bushing is installed by positioning the left and right halves around the outer circumference of the shaft and then the alignment pins are seated within the corresponding bores so that the excluder bushing defines an annular ring that surrounds the shaft. The excluder bushings also have the appropriate O-rings positioned within the grooves in the outer circumference of the bushing halves wherein the assembled bushing (10, 10-1, 110 or 110-1) is then press fitted into its respective seal chamber with the O-ring being compressed and frictionally engaged with the interior surface of the seal chamber to prevent axial and circumferential displacement of the bushing during operation.

It will be understood that the flow slots preferably are linear and have rectangular cross-sectional shapes, but some curvature may be provided. For example, the slots could be arcuate rather than linear.

Thereafter, the mechanical seal 30 is installed in position to prevent leakage of process fluid along the shaft. During operation, the relative rotation of the shaft 25 or 102 relative to the excluder bushing radially adjacent thereto generates a viscous flow of process fluid which flow is controlled by the circumferential flow slots and the tangentially angled flow slots. Generally, the process fluid flows circumferentially through the circumferential flow slots with the scarf cuts redirecting this flow at a tangential angle to a next adjacent one or a downstream one of these circumferential slots until such time as the process fluid is discharged from the inboard end of the excluder bushing. Thus, the inward flow of process fluid generally occurs within the flow slots while a return flow of clean process fluid occurs in the radial gap between the outer shaft service and the inside face of the slot wall. This excluder bushing of the invention provides improved performance and lengthens the overall life of the components being protected such as the mechanical seal.

Although particular preferred embodiments of the invention have been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention. 

1. In a solids excluder bushing for equipment having a rotating shaft, said equipment including an equipment housing having an interior which includes said shaft extending axially therethrough and defines first and second chambers disposed axially next to each other, a process fluid being disposed within said first and second chambers, comprising the improvement wherein said bushing has an annular shape which surrounds said shaft with said bushing being disposed between said first and second chambers, and said bushing includes an inside bushing surface which faces radially inwardly toward an outer shaft surface of said shaft, said inside bushing surface including flow inducing formations which generate a flow of process fluid from said second fluid chamber toward said first fluid chamber to remove solid matter contained in said process fluid from said second chamber, said flow inducing formation comprising at least one circumferential flow slot which extends circumferentially along said inside bushing surface and are separated from each other by circumferentially extending slot walls, said flow inducing formations further comprising at least one angled flow slot extending through each said slot wall to generate an angled flow of said process fluid through said slot wall to generate a fluid flow in response to shaft rotation which displaces said process fluid from said second chamber into said circumferential flow slots and then into said first chamber.
 2. The solids excluder bushing according to claim 1, wherein said inside surface of said bushing is spaced radially from said outer shaft surface to permit a return flow of said process fluid axially from said first chamber to said second chamber.
 3. The solids excluder bushing according to claim 1, wherein said circumferential flow slot and said slot walls are circumferentially continuous.
 4. The solids excluder bushing according to claim 3, wherein a downstream end of each said angled flow slot is circumferentially spaced away from an upstream end thereof in the direction of shaft rotation and is disposed axially farther away from said second chamber than said upstream end.
 5. The solids excluder bushing according to claim 1, wherein a mechanical seal is disposed within said second chamber and said solids excluder bushing draws said process fluid and solids associated therewith away from said mechanical seal.
 6. The solids excluder bushing according to claim 1, wherein said inside bushing surface is disposed closely adjacent to said shaft surface such that said fluid flow of said process fluid is generated by shaft rotation which generates a circumferential flow of said process fluid through each said circumferential flow slot and an angled flow through each said angled flow slot.
 7. The solids excluder bushing according to claim 6, wherein at least one said angled flow slot has an upstream open end which opens into said second chamber for receiving process fluid therefrom and at least one said angled flow slot has a downstream open end which opens toward said first fluid chamber for discharging said process fluid from said solids excluder bushing during shaft rotation.
 8. The solids excluder bushing according to claim 1, wherein said solids excluder bushing includes at least three said slot walls and at least two said circumferential flow slots separated from each other and from said first and second chambers by said slot walls wherein each said slot wall includes at least one said angled flow slot extending therethrough.
 9. The solids excluder bushing according to claim 1, wherein said solids excluder bushing includes one said circumferential flow slot separated axially from said first and second chambers by respective ones of said slot walls wherein each said slot wall includes at least one said angled flow slot therein.
 10. A solids excluder bushing for mounting to an equipment housing which surrounds a rotatable, axially-elongate shaft to generate a flow of process fluid from an outboard chamber to an inboard chamber, said solids excluder bushing comprising: an annular ring defined by an outer circumferential surface, an inner circumferential surface, an outboard end and an inboard end, said inner circumferential surface having flow inducing formations which generate a flow of said process fluid axially between said inboard and outboard chambers, said flow inducing formations comprising a plurality of slots which extend circumferentially in side by side relation and open radially inwardly toward a surface of said shaft wherein said circumferential flow slots are separated axially from each other and from said inboard and outboard chambers by intermediate slot walls, said flow inducing formations further including transverse flow slots which extend axially through said slot walls wherein at least one said transverse flow slot is provided in each said slot wall between an axially adjacent pair of said circumferential flow slots to permit a flow of said process fluid from an upstream one of said circumferential flow slots to a downstream one of said circumferential flow slots, said inner circumferential surface adapted to be disposed closely adjacent to said outer shaft surface such that shaft rotation effects circumferential flow of said process fluid through said circumferential flow slots and a simultaneous axial flow of said process fluid between said upstream and downstream ones of said circumferential flow slots.
 11. The solids excluder bushing according to claim 10, wherein said circumferential flow slots are circumferentially continuous.
 12. The solids excluder bushing according to claim 11, wherein said outer circumferential surface includes an elastomeric member which is adapted to frictionally engage an opposing surface within an equipment housing to maintain said solids excluder bushing stationary during shaft rotation.
 13. The solids excluder bushing according to claim 12, wherein said elastomeric member is an O-ring.
 14. The solids excluder bushing according to claim 10, wherein said bushing is split so as to be defined by first and second bushing sections which couple together to define said annular ring.
 15. The solids excluder bushing according to claim 10, wherein said transverse flow slots extend between upstream and downstream ends thereof, said transverse flow slot extending circumferentially and axially away from said upstream end in the direction of shaft rotation such that said transverse flow slot is angled relative to said circumferential flow slot.
 16. A solids excluder bushing for mounting to an equipment housing which surrounds a rotatable shaft to generate a flow of process fluid from an outboard chamber to an inboard chamber, wherein said bushing is an annular ring having opposite first and second ends and an inner circumferential surface extending axially therebetween, said inner circumferential bushing including slot walls that project radially inwardly and extend circumferentially in side by side relation to define one or more circumferential flow slots which open radially inwardly toward the shaft, each said slot wall further including at least one tangentially angled flow slot which extends between and opens into any of said circumferential flow slots adjacent thereto wherein each said angled flow slot between an adjacent pair of circumferential flow slots permits fluid flow from an upstream one of said circumferential flow slots to a downstream one of said circumferential flow slots, at least one of said angled flow slots opening axially from a first end of said bushing and another said angled flow slot opening axially from an opposite end of said bushing to permit discharge of said process fluid axially therethrough during shaft rotation, said inner circumferential surface being configured to be in close association with an outer shaft surface such that movement of the outer shaft surface relative to said inner circumferential surface generates a circumferential flow of said process fluid wherein said process fluid moves circumferentially through said circumferential flow slots and also through said angled flow slots to move said process fluid from said first bushing end toward said second bushing end.
 17. The solids excluder bushing according to claim 16, wherein said circumferential flow slots and said angled flow slots are deep grooves which permit the flow of said process fluid as well as solids associated with said process fluid.
 18. The solids excluder bushing according to claim 17, wherein said bushing is adapted for non-movable engagement with a support housing of the equipment to prevent rotation of said solids excluder bushing during shaft rotation.
 19. The solids excluder bushing according to claim 16, wherein said inner circumferential surface is adapted to be spaced outwardly from a shaft surface to permit axially circulation of said process fluid along said shaft surface in the direction opposite to the direction of axial fluid flow generated through said circumferential and angled flow slots.
 20. The solids excluder bushing according to claim 16, which is defined by a plurality of semi-circular bushing sections joined in end to end relation to define said annular ring. 